1. Field of the Invention
The invention relates to a fuel cell system and control method therefore, which supply electric power, output from a fuel cell, to a motor.
2. Description of Related Art
There is known a system of this type, in which a fuel cell and an electrical storage device (such as a secondary battery) are connected in parallel with a motor, a boost DC-DC converter (hereinafter, referred to as “FC boost converter”) is provided between the motor and the fuel cell and a boost DC-DC converter (hereinafter, referred to as “battery boost converter”) is provided between the motor and the electrical storage device (for example, see Japanese Patent Application Publication No. 2007-318938 (JP 2007-318938 A)). Furthermore, there is known such a system that is configured to stop boost operation of the FC boost converter or battery boost converter depending on circumstances (for example, see Japanese Patent Application Publication No. 2007-209161 (JP 2007-209161 A), Japanese Patent Application Publication No. 2010-45889 (JP 2010-45889 A), Japanese Patent Application Publication No. 2010-124689 (JP 2010-124689 A), and the like).
In the thus configured existing systems, when boost operation of each of the above described converters is stopped without any discretion, voltage control in the system conversely collapses. This may lead to overcurrent or overvoltage in some cases.